Suppose site A has two inner pages in which inner page url is different but title,content and description are same. We use canonical tag to avoid spamming.
Anne, check out the Google Help Centre guide on REL Canonical. Basically you put a piece of code in the <head> section of your web page, and it tells Google where the original page is. So if the REL canonical is the same as the current URL you are looking at the original, but if the REL canonical points elswhere you know it isn't the original page - so Google can avoid penalising people for duplicate content an correctly attribute the original page with the appropriate Google ranking.
Mainly use canonical tag for avoid to duplicate content, if your web pages is same than we use canonical tag.
When same website open with different urls, then there is a canonical issue. It divides our page rank.
Hope you have found as, some sites with www version, non www version and some sites along with index.htm extension. These are said to be Canonical Url. In this case the link juice can be split. To avoid this issue, we need to redirect the website either with www version or non www version permanently. For this 301 redirection can be used. 301 redirection can always be search engine friendly. If the sites met with canonical error the search engines will treat as different urls.. so its always better to rectify the canonical error
I have never used this kind of method for prevent duplicate content. But thanks all of you guys for this information. There i have learn something new in seo. Thanks
Well dear canonical is called that two urls which have same content and same design like "www.sitename.com" and sitename.com these are two urls but one site but according to Google crawler these are two duplicate sites and it is called canonical issue. To solve this issue you have to make htaccess file in your domain cpanel and then paste this code in your page before </head> <link rel="canonical" href="http://www.yoursitename.com" /> if you cannot do this then visit this site for further help, www.engmineseo.com
As many have already posted, the canonical tag tells google that although the content on this site is duplicate of another that the other is the original. This is also sometimes helpful within Wordpress since there can be many urls pointing to a post within many categories. For example: "www.sitename.com/category1/post" can also be reached at "www.sitename.com/category2/post" but <link rel="canonical" href="http://www.sitename.com/category1/post" /> would state that it was the original url and give credit to that one so as not to have duplicate content for SEO purposes.
The canonical tag lets us tell the search engines that a specific URL is a duplicate of another URL, another web page on your website